1. Technical Field
The present invention relates to the structure of a ramp, which retracts a suspension arm, which holds magnetic heads for reading or writing information from or to a recording disk of an information recording disk apparatus being rotated at high speeds, from the recording disk when the disk is not operated and then holds the retracted suspension arm.
2. Description of the Related Art
In information recording apparatuses employed in information processors such as computers or the like, the hard disk apparatus is an information recording disk apparatus employing a magnetic recording disk, which rotates at high speeds, as a recording medium. The hard disk apparatus rotates a plurality of magnetic recording disks (hereinafter stated as xe2x80x9crecording disksxe2x80x9d) at high speeds and reads and writes information by magnetic heads provided to correspond to the upper and lower surfaces of each recording disk.
The magnetic head used in the hard disk apparatus is supported by a suspension arm that is driven by an actuator, and moves over the recording disk at high speeds. Unless the magnetic head crashes, it never touches the recording disk, and the high rotational speed of the recording disk creates a thin cushion of air that floats the magnetic head off the disk by a very small amount.
The magnetic head is required not to contact the recording disk even when the disk does not rotate. This is because there is a possibility that the magnetic head will be fixedly attached on the surface of the recording disk, if the magnetic head contacts the disk for a long period of time when the disk is not rotating. If the magnetic head is fixedly attached on the disk surface, the start of rotation of the recording disk will separate the fixedly attached portion from the disk surface and destroy the disk surface.
The magnetic head is also required not to contact the recording disk even for such a short time that the magnetic head is not fixedly attached on the disk surface. For example, in the case where the magnetic head is contacted with the recording disk not being rotated, there is a possibility that the disk surface will be shaved due to friction which occurs when the magnetic head contacts the disk, during the time that the disk starts rotating and reaches a predetermined rotational speed. Generally, in order to float the magnetic head off the recording disk, the disk is required to have reached the predetermined rotational speed.
As described above, it is necessary that the magnetic head remains retracted from the recording disk until the disk reaches the predetermined rotational speed. For this reason, a magnetic-head holding mechanism called a ramp is recently known. The ramp is used to retract the magnetic head and the suspension arm from the recording disk and hold the retracted magnetic head, when the recording disk is less than the predetermined rotational speed.
The hard disk apparatuses in recent years are provided with a ramp that functions as a saving place for holding the magnetic head retracted from the recording disk during the stop of rotation of the disk and during low rotation. Such a hard disk apparatus unloads the magnetic head to the ramp if the rotational speed of the disk is reduced and becomes less than a rotational speed at which the magnetic head cannot float, and loads the magnetic head over the disk if the rotational speed of the disk rises and reaches an enough rotational speed to float the magnetic head. The method of unloading or loading the magnetic head from or to the ramp, as described above, is called a ramp loading method.
The ramp is molded and manufactured from high polymer material. The ramp is screwed to the housing of the hard disk apparatus and subjected to stress in the direction of compression in which it is pushed against the housing by the tightening torque of the screw. Therefore, if a long period of time passes, creep deformation which is plastic deformation will occur in the ramp formed from high polymer material.
In addition, the information recording disk apparatus has incorporated a motor, a driver circuit or the like to rotate the recording disk at high speeds, so it cannot be avoided that the temperature in the inside of the information recording disk apparatus will rise because of heat generated by the components. Therefore, the surrounding temperatures of the ramp also rise during high rotation of the recording disk and decrease and approach normal temperature during the stop of rotation of the recording disk. That is, the ramp is used under the condition that-temperature changes in a cycle. In that case, as also evident in the field of reliability tests that a temperature cycle accelerates time, for example, creep deformation is liable to occur with the passage of time.
FIG. 7 is a plan view showing a conventional magnetic recording disk apparatus employing the ramp. A magnetic recording disk apparatus 10 illustrated in FIG. 7 houses recording disks 17, a rotary actuator assembly 12, a voice coil motor 16, and a ramp 20 in the inside of a housing 11 and forms an airtight space in the inside. Each of the recording disks 17 has magnetic recording layers on the upper and lower surfaces and are stacked and fixedly attached to a spindle shaft 18. Each disk is rotated integrally with the spindle shaft 18 by a spindle motor (not shown). The upper and lower surfaces of each of the recording disks 17 are used as the information recording surfaces, and a dedicated magnetic head (not shown) is employed with respect to each surface. The actuator assembly 12 has suspension arms 14 stacked by the same number as the information recording surfaces and is supported by a pivot shaft 13. A slider 19 is attached to the front end of each suspension arm 14 and provided with magnetic heads that scan the upper and lower information recording surfaces of each disk. Furthermore, a lifting protrusion 15 is attached to the front end of the suspension arm 14.
The actuator assembly 12 is rotated on the pivot shaft 13 by the voice coil motor 16 so that the slider 19 with the magnetic heads is loaded over the surface of the recording disk 17 or unloaded to the ramp 20. The suspension arms 14 are formed from elastic material and urged in the direction in which each slider 19 attached to each suspension arm 14 approaches the corresponding disk surface of the recording disk 17. If the force to float the slider 19, created by rotation of the recording disk 17, is balanced with the elastic force of the suspension arm 14, the slider 19 will be floated a predetermined distance off the surface of the recording disk 17 being rotated. The ramp 20 is fixed to the housing 11 of the magnetic recording disk apparatus 10 by employing a screw 31, at a position where the front ends of the ramp are near the recording disks 17 and alternately extend into between the disks without contacting any disks.
FIG. 8A is a perspective view showing a conventional ramp where all parts have been molded en bloc by employing high polymer material containing polytetrafluoroethylene (PTFE), and FIG. 8B shows another conventional ramp reinforcing a screw hole with a metal sleeve in the ramp of FIG. 8A. Note that FIGS. 8A and 8B show the ramps of the type that holds suspension arms in the case of stacking three double-sided recording disks.
As illustrated in FIG. 8A, the conventional ramp 20 is configured by an attaching portion 21 and an arm holding portion 22. The attaching portion 21 has a screw hole 25 for fixing the ramp 20 to the housing 11 of the information recording disk apparatus 10 by employing a screw 31. The arm holding portion 22 has storing portions 27 and guide portions 28. Each of the storing portions 27 holds the slider 19 retracted from the corresponding recording disk 17, the slider 19 having the magnetic heads for performing read and write operations on the recording disk 17. Each guide portion 28 makes it easy for the suspension arm 14 to move in and out of the storing portion 27 by sliding the lifting protrusion 15. The attaching portion 21 and the arm holding portion 22 are molded en bloc by a single injection molding operation, with high polymer material containing PTFE. The attaching portion 21 is configured by the screw hole 25 and a bracket 23 surrounding the screw hole 25. The arm holding portion 22 is constructed by the storing portions 27 and guide portions 28, which correspond to the upper and lower surfaces of the recording disks 17, and a support portion 24 which supports the storing portions 27 and guide portions 28 so that they are disposed in the direction in which the recording disks 17 are stacked. The storing portions 27 and the guide portions 28 are provided not only on the upper side of each disk of the recording disks 17 shown in FIG. 8A but also on the lower side and are formed symmetrically with respect to a plane X-Y dividing the disk horizontally into two parts. The circumferential edges of the recording disks 17 are partially inserted into openings 26. That is, each disk edge is interposed between the front edges 29 of the corresponding guide portions 28 without contacting any front edges. The ramp 20 is fixed to the housing 11 by the screw 31 so that the aforementioned positional relationship between the disk edges and the guide portions 28 is satisfied. If the actuator assembly 12 is retracted from the recording disk 17, the lifting protrusion 15 attached to the suspension arm 14 is lifted near the front edge 29 of the guide portion 28, slides against the guide portion 28, and is stored in the storing portion 27. On the other hand, if the actuator assembly 12 moves toward the recording disk 17 in the opposite direction, the lifting protrusion 15 moves out of the storing portion 27, slides against the guide portion 28, and moves over the disk surface from the front edge 29 of the guide portion 28.
In the case where the ramp 20 shown in FIG. 8A is fixed to the housing 11 of the information recording disk apparatus 10 by tightening the screw 31, stress will be accumulated near the screw hole 25 of the attaching portion 21. The stress deforms the peripheral portion with the passage of time and causes errors to occur in the dimension of each part of the ramp 20. That is, creep deformation will occur in the ramp 20 when it is fixed with the screw 31.
The portion where creep deformation becomes a problem particularly in the ramp 20 is the screw hole 25 and front edge 29 of the guide portion 28.
Since the tightening stress of the screw 31 is reduced in the screw hole 25 because of creep deformation, there will arise a problem that the ramp 20 in the information recording disk apparatus 10 loosens. In addition, the front edge 29 of the guide portion 28 needs to be installed so that it does not touch the recording disk and is not too away from the disk, in order to smoothly guide the suspension arm 14 (lifting protrusion 15), positioned over the disk being rotated at high speeds, to the storing portion 27 and, conversely, in order to smoothly guide the suspension arm 14 (lifting protrusion 15), stored in the storing portion 27, to the disk being rotated at high speeds. That is, the front edge 29 of the guide portion 28 needs to be positioned within a predetermined distance perpendicularly away from the recording disk. However, if creep deformation occurs near the screw hole 25 of the attaching portion 21, the front edge 29 of the guide portion 28 will be moved out of a predetermined distance perpendicularly away from the recording disk by the influence of creep deformation. As a result, there will arise a drawback that polymer particles occur, because the ramp 20 is easily contacted with the recording disk by external shock.
To eliminate the aforementioned drawbacks found in the ramp 20, a ramp reinforcing the screw hole 25 with a metal sleeve is known.
Illustrated in FIG. 8B is a ramp 20a reinforcing the screw hole 25 of the ramp 20 shown in FIG. 8A, with a metal sleeve 30.
The ramp 20a is molded with the metal sleeve 30 inserted into the screw hole 25. This can alleviate the stress accumulated near the screw hole 25 when tightening the screw. Therefore, the drawback that the ramp 20a in the information recording disk apparatus 10 loosens can be eliminated. In molding the ramp 20a, however, stress (thermal stress) resulting from a temperature difference during molding is accumulated near the metal sleeve 30 of the ramp 20a, because injection molding is performed under the condition that the metal sleeve 30 at normal temperature is placed in a metal mold managed in a predetermined high-temperature state. Particularly, when the temperature of the metal mold during molding rises to 80 to 90xc2x0 C. near the upper limit of the operating temperature of the hard disk apparatus and then returns to room temperature, the thermal stress causes deformation to occur in the front edge 29 of the guide portion 28, as with the tightening stress of the screw. Furthermore, the metal sleeve 30 in the ramp 20a produces metal powder because it slides against the screw 31, when molding is performed with the metal sleeve 30 inserted in the screw hole 25 and when the ramp 20a is screwed to the housing 11. The occurrence of metal powder must be suppressed to the utmost, since there is a possibility that it will have an adverse effect on the magnetic heads, recording disks 17, etc., of the information recording disk apparatus 10. In addition, the great thermal expansion of resin around the metal sleeve 30 has influence on the guide portions 28. Therefore, applying the metal sleeve 30 to the ramp 20a is effective in order to alleviate the tightening stress of the screw, but is. unsuitable from the standpoint of the occurrence of thermal stress and the occurrence of thermal expansion and metal powder.
Next, as to the fact that the front edge 29 of the guide portion 28 is moved out of a predetermined distance perpendicularly away from the recording disk 17, a further description will be described with the drawings.
FIG. 9 illustrates the section of the ramp 20a and suspension arm 14 of FIG. 8B taken along line Axe2x80x94A of FIG. 7 in the direction of arrow Z. In FIG. 9, the ramp 20a has been fixed to the housing 11 of the information recording disk apparatus 10 by the screw 31. Also, three recording disks 17 (A, B, C) have been partially inserted into the ramp 20a without contacting the ramp 20a, and the suspension arms 14 have been retracted from the recording disks 17 to the guide portions 28. Note that in FIG. 9, there are spaces for a clear understanding of components; however, the lower surface of the bracket 23 and the lower surface of the support portion 24 are in intimate contact with the housing 11 and the ramp 20a is supported by the housing 11.
If the front edge 29 of the guide portion 28 is moved out of a predetermined distance perpendicularly away from the recording disk surface, there are cases where the gap distance (L1up) between the upper surface of the recording disk and the slot of the ramp 20a (opening 26) becomes unequal to the gap distance (L1down) between the lower disk surface and the slot. In the case where either L1up or L1down becomes extremely small, the recording disk is easily contacted with the ramp 20a by external shock during operation of the hard disk apparatus and therefore there is a possibility that reading and writing of information will be disturbed. Since the distances L1up and L1down become unequal, a great difference will occur between the loading and unloading positions over the recording disk which load and unload the sliders (magnetic heads) provided over the upper and lower disk surfaces. The recordable area on the recording disk is determined by the magnetic head in which the distance L2 is longer. That is, if the slider (magnetic head) loading and unloading positions over the recording disk are moved in the radially inner direction of the disk, the recordable area on the disk will diminish, and in the case of the same recording density, there will arise a disadvantage that the entire capacity is reduced. In addition, as an extreme example of the hard disk apparatus, there is a possibility that the data stored on the disk cannot be read out because of movement of the front edge 29 of the guide portion 28.
Notice that FIG. 9 illustrates both the lifting protrusion 15 supported by the guide portion 28 and the lifting protrusion 15 positioned over the disk, for a clear understanding of the present invention.
The drawback that the front edge 29 of the guide portion 28 is moved out of a predetermined distance perpendicularly away from the disk surface is prone to arise when the recording disk 17 is rotating at high speeds, i.e., when the inside of the information recording disk apparatus 10 is in a high-temperature state. This is because it is considered that the direction of deformation is changed by the influence of the aforementioned thermal stress or the tightening stress of the screw, when the front edge 29 of the guide portion 28 in the ramp 20a is deformed due to its thermal expansion during high rotation of the recording disk 17, since high polymer material has a thermal expansion coefficient several times ten to twenty times metal material.
The drawback that the front edge 29 of the guide portion 28 is moved out of a predetermined distance perpendicularly away from the disk surface 17 is more easily liable to occur as the number of the recording disks 17 to be stacked within the information recording disk apparatus 10 becomes greater. This is that the dimension of the ramp 20a becomes greater in the direction in which a plurality of recording disks are stacked, if the number of recording disks increases. For example, in the case where six front edges 29 in FIG. 9 are expressed as A1, A2, B1, B2, C1, and C2 in order from the upper side of the magnetic recording disk apparatus 10 to the lower side contacting the housing 11, the degree that the front edges 29 (A1, A2, B1, B2, C1, and C2) of the guide portions 28 are deformed due to their thermal expansion is increased, because the distance L3 between the front edge 29 (C2) of the guide portion 28 corresponding to the lower surface of the lowermost disk 17(C) and the front edge 29 (A1) of the guide portion 28 corresponding to the upper surface of the uppermost disk 17(A) increases.
FIG. 10 shows the degree that the front edge 29 of the guide portion 28 of the conventional ramp shown in FIGS. 8B and 9 is deformed because of temperature.
In FIG. 10, the degrees of deformation of the six front edges 29 (A1, A2, B1, B2, C1, and C2) in FIG. 9 were measured according to surrounding temperature changes.
As shown in FIG. 10, the degree of deformation of the front edge C1 is on the side of +, while the degree of deformation of the front edge B2 is slightly on the side of xe2x88x92. The front edge C1 in this case is deformed upward and the front edge B2 is deformed slightly downward. Therefore, the gap between the front edge C1 and the front edge B2 narrows with a rise in temperature, and it is understandable that the gap between the front edge B1 and the front edge A2 narrows similarly. Since these gaps diminish, in the worst case the adjacent suspension arms 14 between the front edges C1 and B2 or between the front edges B1 and A2 contact each other during movement and metal particles are produced within the hard disk apparatus. The occurrence of metal particles often destroys the data stored on the disk.
In FIG. 10, the gap between the front edge A1 and the front edge C2 is approximately 85 xcexcm (difference xcex94L due to deformation of distance L3 of FIG. 9) in case of 100xc2x0 C. The value of this gap becomes greater if the number of recording disks 17 to be stacked within the information recording disk apparatus 10 is increased, so it becomes a graver problem.
Accordingly, it is an object of the present invention to provide a ramp in which deformation and loosening because of creep deformation do not occur and metal powder does not occur.
Another object of the invention is to provide a ramp which is capable of reducing the degree of deformation of the front edge of the guide portion caused in the direction in which recording disks are stacked.
In a ramp to store suspension arms which correspond to both sides of multiple double-sided recording disks, still another object of the invention is to provide a ramp where mechanical interference does not occur in adjacent suspension arms even when temperature rises, while reducing the degree of deformation of the front edge of the guide portion due to heat by only resin molding without employing a metal component such as a metal sleeve.
To attain the aforementioned objects, there is provided a ramp, which is used in an information recording disk apparatus having a suspension arm to hold a magnetic head for writing or reading information to or from a recording disk, for retracting the suspension arm from the recording disk and holding the suspension arm. The ramp comprises: a plurality of blocks with a connecting surface, each block being formed from a different high polymer material; and locking means in undercut form formed in each of the connecting surfaces. The blocks are connected mechanically and united in one by the locking means.
In the ramp for an information recording disk apparatus according to the present invention, the ramp is constructed by (1)an attaching portion molded with high polymer material, which is slight in creep deformation and small in thermal expansion coefficient, so that it is provided with a screw hole for fixing the ramp to a housing of the information recording disk apparatus by a screw and (2) an arm holding portion molded with high polymer material whose fiction coefficient is small, the arm holding portion having a storing portion to hold the suspension arm retracted from the recording disk and also having a guide portion against which the suspension arm slides so that it is easily moved in and out of the storing portion. The attaching portion and the arm holding portion are united in one by the locking means in undercut form.
In the ramp for an information recording disk apparatus according to the present invention, creep deformation occurs less in the high polymer material that is employed in the attaching portion than in the high polymer material that is employed in the arm holding portion. In addition, the thermal expansion coefficient of the high polymer material which is employed in the attaching portion is smaller than that of the high polymer material which is employed in the arm holding portion.
In the ramp for an information recording disk apparatus according to the present invention, the high polymer material that is employed in the attaching portion is selected from among polyetherimide (PEI), polyimide (PI), polycarbonate (PC), polyethersulphone (PES), polyphenylenesulfide (PPS), and high polymer material mixed with glass fibers or carbon fibers. In the ramp for an information recording disk apparatus according to the present invention, the high polymer material with a small friction coefficient, which is employed in the arm holding portion, is liquid crystal polymer (LCP) or contains polytetrafluoroethylene (PTFE).
In the ramp for an information recording disk apparatus according to the present invention, the high polymer material which is employed in the attaching portion and the high polymer material which is employed in the arm holding portion have the same temperature range in a temperature condition required of a metal mold for molding both materials.
In accordance with the present invention, there is provided a method of manufacturing a ramp that retracts a suspension arm, which holds a magnetic head for writing or reading information to or from a recording disk, from the recording disk and holds the suspension arm. The method comprises the steps of: designing the ramp so that it is constructed by a plurality of blocks; molding the blocks subsequently with different high polymer materials; molding an undercut in a connecting surface of the first molded block which contacts the second molded block; and causing the undercut to function as part of a metal mold in molding the second molded block. According to this manufacturing method, the blocks that are molded with different high polymer materials are united in one.
In the ramp for an information recording disk apparatus according to the present invention, the temperature of the metal mold is higher than 90xc2x0 C. which is higher than the highest temperature that a hard disk apparatus reaches when it is installed or in use. At temperatures less than this, the distortion or stress, stored in the inside of the ramp, is difficult to release. Therefore, ramps molded at temperatures less than 90xc2x0 C. can be easily discriminated, because ramp deformation is conspicuous if the ramps are raised to 90xc2x0 C.
In the ramp manufacturing method according to the present invention, the metal mold for molding a plurality of blocks molds one block at a first molding position, then rotates along with the molded block to a second molding position and molds another block. According to the present invention, there is provided an information recording disk apparatus comprising: a rotary actuator assembly having a suspension arm connected thereto; a plurality of magnetic disks stacked; a ramp, disposed near the magnetic disks, for retracting the suspension arm; and a housing to house the actuator assembly, the magnetic disks, and the ramp. The ramp as set forth in any one of claims 1 to 12 is fixed on the housing by an attaching screw.